Dual poppet pressure relief valve with vacuum adaptor capability

Abstract

A pressure relief valve is disclosed with a first stage valve that is in series with a second stage valve, with an enclosed cavity between the first stage valve and the second stage valve. The first stage valve relieves pressure from an enclosure into the enclosed cavity between the stages, when the pressure is above a cracking pressure of the first stage valve. The second stage relieves pressure from the enclosed cavity when the pressure is above the cracking pressure of the second stage valve.

What is claimed is: 
     
       1. A dual poppet pressure relief valve (PRV) comprising:
 an internal poppet valve; 
 an external poppet valve; 
 a coupling between the internal poppet valve and the external poppet valve, the coupling comprising:
 a pin extending through a bore in the internal poppet valve and extending through a bore in the external poppet valve; 
 
 an external spring which biases the external poppet into a closed position; and 
 an internal spring which biases the internal poppet into a closed position wherein the pin is retained within the bore within one or more windings of the internal spring. 
 
     
     
       2. The dual poppet PRV of  claim 1 , wherein an inner diameter of the bore in the external poppet valve is larger than an external diameter of the pin. 
     
     
       3. The dual poppet PRV of  claim 1 , wherein a first cracking pressure of the internal poppet valve is different from a second cracking pressure of the external poppet valve. 
     
     
       4. The dual poppet PRV of  claim 3 , wherein a difference between the first cracking pressure and the second cracking pressure is 3-4 psi. 
     
     
       5. The dual poppet PRV of  claim 3 , wherein a difference between the first cracking pressure and the second cracking pressure is 5-10 psi.